De-embedding devices under test

ABSTRACT

A system for de-embedding electrical characteristics to obtain the intrinsic electrical characteristics of a device under test. The system includes obtaining a set of S parameter data from measurements of a thru test structure and partitioning that set into a set of input S parameters and a set of output S parameters. The set of input S parameters and the set of output S parameters are converted to sets of input ABCD parameters and output ABCD parameters, respectively. An inverse matrix of the set of input ABCD parameters is cascaded with a matrix of a set of ABCD parameters representative of the electrical characteristics of a test structure including the device under test. The resultant matrix is then cascaded with the inverse matrix of the set of output ABCD parameters to obtain a set of device ABCD parameters representative of the intrinsic electrical characteristics of the device under test.

BACKGROUND OF THE INVENTION

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.

1. Field of the Invention

This invention relates in general to electronic circuits and in particular to de-embedding devices.

2. Description of the Related Art

In the design of integrated circuits such as e.g. high-frequency/RF integrated circuits, it is desired that only the intrinsic characteristics of the underlying semiconductor devices be incorporated in the design process. Typically, determination of the intrinsic characteristics is accomplished in a manner such that unwanted parasitics are introduced into the characterization process, due to the process of fabricating the associated test devices. De-embedding is a process that is utilized to remove the effects of the parasitics from the characteristics of a device under test.

FIGS. 1-4 are functional schematics of 2-port test structures typically used in prior art de-embedding processes. FIG. 1 is a schematic representation of test structure 101 that includes a transmission configured two terminal device under test (DUT) 111, shown as a two-port network. Examples of such devices include capacitors, diodes, inductors, resisters, or any other two terminal device. In one embodiment, DUT 111 is fabricated on a substrate of a semiconductor wafer with input port 103 and output port 107 located on the wafer surface for radio frequency (rf) characterization.

FIG. 2 is a schematic representation of a “thru” test structure typically used for de-embedding the electrical characteristics of DUT 111. It is desirable that test structure 201 have the same electrical length and port characteristics as test structure 101 exclusive of DUT 111.

FIG. 3 is a schematic representation of a “short” test structure typically used for de-embedding the electrical characteristics of DUT 111. It is desirable that test structure 301 have the same port characteristics and the same electrical length as test structure 101, but with rf “shorts” at locations corresponding to the locations of port-1 and port-2 of DUT 111.

FIG. 4 is a schematic representation of an “open” test structure typically used for de-embedding the electrical characteristics of DUT 111. It is desirable that test structure 401 have the same port characteristics and the same electrical length as test structure 101, but with rf “opens” at locations corresponding to the locations of port-1 and port-2 of DUT 111.

Test structures 201, 301, and 401 are constructed from the same fabrication process as test structure 101 of FIG. 1.

A prior art process of de-embedding typically involves the collection of scattering (S) parameters on test structures 101, 201, 301, and 401. The S parameters from test structure 101 are then modified to remove the effects of parasitics associated with test structure 101 as determined from the S parameters collected from test structures 201, 301, and 401. With some prior art de-embedding processes, test structure 201 may not be required.

The process of de-embedding described above requires the fabrication of three additional test structures (201, 301, and 401). Each additional test structure requires/occupies additional wafer area and increases testing time and complexity. What is desired is an improved process of de-embedding.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood, and its numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings.

FIG. 1 is a schematic representation of a test structure used in a prior art de-embedding process.

FIG. 2 is a schematic representation of a test structure used in a prior art de-embedding process.

FIG. 3 is a schematic representation of a test structure used in a prior art de-embedding process.

FIG. 4 is a schematic representation of a test structure used in a prior art de-embedding process.

FIG. 5 is a schematic representation of a test structure used in one embodiment of a de-embedding process according to the present invention.

FIG. 6 is a schematic representation of a test structure used in one embodiment of a de-embedding process according to the present invention.

FIG. 7 is a flow diagram setting forth one embodiment of a de-embedding process according to the present invention.

FIG. 8 is a schematic representation illustrating one embodiment of a partitioning of the electrical characteristics of a thru test structure into electrical characteristics of two two-port networks according to the present invention.

FIG. 9 shows one embodiment of equations setting forth constraints in partitioning the electrical characteristics of a thru test structure into electrical characteristics of two two-port networks according to the present invention.

FIG. 10 sets forth one embodiment of an equation for obtaining intrinsic characteristics of a device under test according to the present invention.

FIG. 11 is a flow diagram setting forth one embodiment of a method for design and fabricating an integrated circuit according to the present invention.

FIG. 12 is block diagram of one embodiment of a system for obtaining intrinsic characteristics of a DUT according to the present invention.

The use of the same reference symbols in different drawings indicates identical items unless otherwise noted.

DETAILED DESCRIPTION

The following sets forth a detailed description of a mode for carrying out the invention. The description is intended to be illustrative of the invention and should not be taken to be limiting.

FIG. 5 is a schematic representation of test structure 501 that includes a transmission configured two terminal device under test (DUT) 511. DUT 511 is a device in which it is desired to obtain its intrinsic properties. Examples of such devices include capacitors, diodes, inductors, resisters, or any other two terminal device in an integrated circuit. Circuit 513 represents the parasitics of the structures between input port 503 and DUT 511, and circuit 515 represents the parasitics of the structures between output port 507 and DUT 511.

In one embodiment, DUT 511 is fabricated on the substrate of a semiconductor wafer with input port 503 and output port 507 located on the wafer surface for radio frequency (rf) characterization. In one embodiment, ports 503 and 507 are implemented in a ground-signal-ground (GSG) configuration. However, structure 501 may represent test structures having other testing configurations.

FIG. 6 is a schematic representation of a thru test structure 601, exclusive of the DUT, used for de-embedding the electrical characteristics of DUT 511. In one embodiment, test structure 601 is fabricated from the same process as test structure 501 of FIG. 5. Circuit 613 represents the parasitics associated with input port 603 and circuit 615 represents the parasitics associated with the output port 607 of thru test structure 601. In one embodiment, test structure 601 has the same electrical length and port characteristics as test structure 501, exclusive of DUT 511.

FIG. 7 is a flow diagram of setting forth one embodiment of a de-embedding process for obtaining intrinsic characteristics of a DUT. The de-embedding process shown in FIG. 7 involves collecting sets of S parameters from two structures, test structure 501 and thru test structure 601.

In operation 703, S parameters are collected from DUT test structure 501. Referring back to FIG. 5, in one embodiment of operation 703, the input reflection coefficient (S₁₁ DUT), the output reflection coefficient (S₂₂ DUT), the forward transmission coefficient (S₂₁ DUT), and the reverse transmission coefficient (S₁₂ DUT) are obtained from structure 501. In one embodiment, these parameters are obtained by rf characterizations of test structure 501 using a calibrated automatic network analyzer (ANA). See FIG. 12.

In operation 705, S parameters are collected from thru test structure 601. Referring back to FIG. 6, in one embodiment of operation 705, the input reflection coefficient (S₁₁ THRU), the output reflection coefficient (S₂₂ THRU), the forward transmission coefficient (S₂₁ THRU), and the reverse transmission coefficient (S₁₂ THRU) are obtained from structure 601. In one embodiment, these parameters are obtained by rf characterizations of test structure 601 using a calibrated automatic network analyzer (ANA).

In operation 707, the electrical characteristics of thru test structure 601 (as represented by the S parameters obtained from thru test structure 601) are partioned into two sets of 2-port S parameters, an input set and an output set. Each set represents the characteristics of a two-port network.

FIG. 8 represents characteristics of the equivalently partitioned thru network 801. Network 801 includes a two-port input network 809, a two-port output network 811, and a virtual reflectionless node 815. The S parameters of input network 809 and output network 811 are parameters that are partitioned from the S parameters obtained from thru test structure 601. The characteristics of network 809 and network 811 are such that when combined, result in the retention of the electrical characteristics of the thru test structure 601.

Virtual node 815 represents a reflectionless node representative of the point of insertion of a DUT.

FIG. 9 sets forth the conditions for partitioning the electrical characteristics of thru test structure 601 into the S parameters associated with input network 809 and S parameters associated with output network 811. Regarding equation, 901, the input reflection coefficient (S₁₁ IN) of input network 809 is set equal to the measured input reflection coefficient (S₁₁ THRU) of test structure 601. Regarding equation, 903, the output reflection coefficient (S₂₂ OUT) of output network 811 is set equal to the measured output reflection coefficient (S₂₂ THRU) of test structure 601.

Regarding equation 905, the output refection coefficient (S₂₂ IN) of input network 809 and the input reflection coefficient (S₁₁ OUT) of the output network 811 are set such that a zero reflection coefficient (0+j0) results.

Equations 907, 909, 911, 913 establish the transmission characteristics of input network 809 and output network 811. S₂₁ IN is the forward transmission coefficient and S₁₂ IN is the reverse transmission of input network 809. S₂₁ OUT is the forward transmission coefficient and S₁₂ OUT is the reverse transmission coefficient of output network 811. As shown in equations 907 and 911, the magnitude of the forward and reverse transmission coefficients of input network 809 and output network 811 are equal to the magnitude of the forward and reverse transmission coefficients, respectively, obtained from thru test structure 601 raised to a power of 1 over a partitioning factor(X). As shown by equations 909 and 913, the angles of the forward and reverse transmission coefficients of input network 809 and output network 811 are equal to the angles of the forward and reverse transmission coefficients (S₂ THRU and S₁₂ THRU) respectively, divided by the partitioning factor.

X represents the partitioning factor that, in one embodiment, is based on the geometric location of DUT 511 in the test structure 501. Referring back to FIG. 5, in one embodiment, X is calculated as the distance from input port 503 to output port 507 (a+b) divided by the distance from DUT 511 to input port 503 (a). In embodiments where a is equal to b, the X partitioning factor is 2.

In one embodiment where the measured S parameters exist in real and imaginary format, the parameters are converted to magnitude and phase format for implementation of equations 907, 909, 911, and 913. Afterwards, the resultant S parameters are converted back to a real and imaginary format.

Referring back to FIG. 7, in operation 709 the S parameters obtained from DUT test structure 601 and the partitioned characteristics of in network 809 and out network 811 are then converted to transmission (ABCD) parameters using standard conversion format.

In 711, the intrinsic characteristics of DUT 511 are derived (represented in ABCD parameters) using equation 1001 of FIG. 10. DMBD_(ABCD) represents a matrix of the intrinsic characteristics of DUT 511 in ABCD parameters. IN_(ABCD) ⁻¹ represents the inverse matrix of input network 809 characteristics in ABCD parameters. OUT_(ABCD) ⁻¹ represents the inverse matrix of output network 811 characteristics in ABCD parameters. As shown in equation 1001, the intrinsic characteristics of DUT 511 is derived by cascading the inverse matrix of the input network characteristics IN_(ABCD) ⁻¹ with the matrix of measured characteristics obtained from structure 501, and then cascading the resultant matrix with the inverse matrix of the output network characteristics OUT_(ABCD) ⁻¹.

Referring back to FIG. 7, the DUT characteristics (in ABCD parameters) are converted back to S parameters in 713.

Utilizing the above de-embedding process may provide a de-embedding process from which the intrinsic characteristics of a transmission configured two terminal device can be derived from collecting data from only one additional test structure. Accordingly, such a de-embedding scheme may be implemented using less wafer space, require less testing time, and affording the ability to determine the desired characteristics directly via measurement.

FIG. 11 is a flow diagram for fabricating an integrated circuit using the intrinsic characteristics obtained by a process similar to the process set forth in FIG. 9. In 1103, the intrinsic characteristics of devices under test that were obtained from a de-embedding processes similar to that set forth in FIG. 7 are incorporated in a design library. In 1105, the design library is used to produce a design for a circuit. In 1107, the circuit is fabricated from the design produced in 1105.

FIG. 12 is block diagram of one embodiment of a system for obtaining intrinsic characteristics of a DUT according to the present invention. A DUT is located in a test structure 1205 fabricated on the substrate of wafer 1203. A thru test structure 1204 is also located on wafer 1203. Probes 1206 and 1207 are used to facilitate obtaining S parameter data from structure 1204 and structure 1205. The probes are operably coupled to calibrated automatic network analyzer 1209 (ANA). Network analyzer 1209 is controlled by code 1217 running on workstation 1211. Code 1217 is down loaded from storage media of 1217 (e.g. hard drives) of a server 1215 by workstation 1211. In other embodiments, code 1217 may be located on a hardrive of personal computer system or down loaded from a removable media (e.g. CDRom). In other embodiments, code 1217 may be executed by a processor located in network analyzer 1209. In one embodiment, the code is implemented in IC-CAP circuit simulation software sold by AGILENT-EESOF.

Set forth below is one embodiment of software code used for implementing operations 707, 709, 711, and 713 of FIG. 7. The code is written in an adaptation of the BASIC language. This code is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyrights whatsoever.

Below is listed one embodiment of code for partitioning the measured S parameters of a thru-test structure (e.g. 601) into a set of S parameters representative of an input network (e.g. 809).

i1=0  i=0  WHILE i < SIZE(thru)   In_2_port.11[i]=thru.11[i1]   !   !********* S12 *********   ! Rev_Mag.12[i]=(real(thru.12[i1]) {circumflex over ( )}2+imag(thru.12[i1]) {circumflex over ( )}2) {circumflex over ( )}0.5   Mag_In_2_port.12[i]=Rev_Mag.12[i] {circumflex over ( )}var2   !   Rev_Arg.12[i]=imag(thru.12[i1])//real(thru.12[i1])   Angle_In_2_port.12[i]=atn(Rev_Arg.12[i])//var1   !   ! if Angle_In_2_port.12[i] > 0 then   !  Angle_In_2_port.12[i] = Angle_In_2_port.12[i]−1.57   ! end if   ! Real_In_2_port.12[i]=cos(pct_l*Angle_In_2_port.12[i])*Mag_In_2 _port.12[i] Imag_In_2_port.12[i]=sin(pct_l*Angle_In_2_port.12[i])*Mag_In_2 _port.12[i]   ! In_2_port.12[i]=(Real_In_2_port.12[i])+j*(Imag_In_2_port.12[i])   !   !********* S21 *********   ! Fwd_Mag.21[i]=(real(thru.21[i1]) {circumflex over ( )}2+imag(thru.21[i1]) {circumflex over ( )}2) {circumflex over ( )}0.5   Mag_In_2_port.21[i]=Fwd_Mag.21[i] {circumflex over ( )}var2   !   Fwd_Arg.21[i]=imag(thru.21[i1])//real(thru.21[i1])   Angle_In_2_port.21[i]=atn(Fwd_Arg.21[i])//var1   !   ! if Angle_In_2_port.21[i] > 0 then   !  Angle_In_2_port.21[i] = Angle_In_2_port.21[i]−1.57   ! end if   ! Real_In_2_port.21[i]=cos(pct_l*Angle_In_2_port.21[i])*Mag_In_2 _port.21[i] Imag_In_2_port.21[i]=sin(pct_l*Angle_In_2_port.21[i])*Mag_In_2 _port.21[i]   ! In_2_port.21[i]=(Real_In_2_port.21[i])+j*(Imag_In_2_port.21[i])   !   In_2_port.22[i]=0+j0   i1=i1+1   IF i1>=size_thru THEN i1=0   i = i + 1  END WHILE  !  RETURN In_2_port

Below is listed one embodiment of code for partitioning the S parameters of a thru test structure (e.g. 601) into a set of S parameters representative of an output network (e.g. 811).

i1=0  i=0  WHILE i < SIZE(thru)   Out_2_port.11[i]=0+j0   !   !********* S12 ***********   ! Rev_Mag.12[i]=(real(thru.12[i1]) {circumflex over ( )}2+imag(thru.12[i1]) {circumflex over ( )}2) {circumflex over ( )}0.5   Mag_Out_2_port.12[i]=(Rev_Mag.12[i]) {circumflex over ( )}var2   !   Rev_Arg.12[i]=imag(thru.12[i1])//real(thru.12[i1])   Angle_Out_2_port.12[i]=atn(Rev_Arg.12[i])//var1   !   ! if Angle_Out_2_port.12[i] > 0 then   !  Angle_Out_2_port.12[i] = Angle_Out_2_port.12[i]−1.57   ! end if   ! Real_Out_2_port.12[i]=cos(pct_l*Angle_Out_2_port.12[i])*Mag_Ou t_2_port.12[i] Imag_Out_2_port.12[i]=sin(pct_l*Angle_Out_2_port.12[i])*Mag_Ou t_2_port.12[i]   ! Out_2_port.12[i]=(Real_Out_2_port.12[i])+j* (Imag_Out_2_port.12 [i])   !   !********* S21 ***********   ! Fwd_Mag.21[i]=(real(thru.21[i1]) {circumflex over ( )}2+imag(thru.21[i1]) {circumflex over ( )}2) {circumflex over ( )}0.5   Mag_Out_2_port.21[i]=(Fwd_Mag.21[i]) {circumflex over ( )}var2   !   Fwd_Arg.21[i]=imag(thru.21[i1])//real(thru.21[i1])   Angle_Out_2_port.21[i]=atn(Fwd_Arg.21[i])//var1   !   ! if Angle_Out_2_port.21[i] > 0 then   !  Angle_Out_2_port.21[i] = Angle_Out_2_port.21[i]−1.57   ! end if   ! Real_Out_2_port.21[i]=cos(pct_l*Angle_Out_2_port.21[i])*Mag_Ou t_2_port.21[i] Imag_Out_2_port.21[i]=sin(pct_l*Angle_Out_2_port.21[i])*Mag_Ou t_2_port.21[i]   ! Out_2_port.21[i]=(Real_Out_2_port.21[i])+j*(Imag_Out_2_port.21 [i])   !   Out_2_port.22[i]=thru.22[i1]   i1=i1+1   IF i1>=size_thru THEN i1=0   i = i + 1  END WHILE  !  RETURN Out_2_port

Below is one embodiment of code for converting a set of measured DUT test structure S parameters and sets of S parameters representative of an input network and an output network to sets of ABCD parameters. The code below also obtains the intrinsic characteristics of the DUT in ABCD parameters and converts them back to S parameters.

i1=0  i=0  WHILE i < SIZE(total)   L_dummy_act.11[i]=L_dummy.11[i1]   L_dummy_act.12[i]=L_dummy.12[i1]   L_dummy_act.21[i]=L_dummy.21[i1]   L_dummy_act.22[i]=L_dummy.22[i1]   R_dummy_act.11[i]=R_dummy.11[i1]   R_dummy_act.12[i]=R_dummy.12[i1]   R_dummy_act.21[i]=R_dummy.21[i1]   R_dummy_act.22[i]=R_dummy.22[i1]   i1=i1+1   IF i1>=size_dummy THEN i1=0   i = i + 1  END WHILE  !  PRINT “now do the de-embedding using ABCD matrix manipulation . . . ”  !  xtor=TwoPort(L_dummy_act,“S”,“A”) {circumflex over ( )}−1 * TwoPort(total,“S”,“A”) * TwoPort(R_dummy_act,“S”,“A”) {circumflex over ( )}−1  xtor=TwoPort(xtor,“A”,“S”)  !  RETURN xtor

While particular embodiments of the present invention have been shown and described, it will be recognized to those skilled in the art that, based upon the teachings herein, further changes and modifications may be made without departing from this invention and its broader aspects, and thus, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this invention. 

1. A method for de-embedding a device under test, the method comprising: representing electrical characteristics of a test structure including a device under test using a set of test structure ABCD parameters; representing electrical characteristics of a thru test structure using a set of thru S parameters; partitioning the set of thru S parameters into a first set of partitioned S parameters and a second set of partitioned S parameters; converting the first set of partitioned S parameters into a first set of partitioned ABCD parameters; converting the second set of partitioned S parameters into a second set of partitioned ABCD parameters; and using the first set of partitioned ABCD parameters, the second set of partitioned ABCD parameters, and the set of test structure ABCD parameters to produce a set of device ABCD parameters representative of intrinsic electrical characteristics of the device under test.
 2. The method of claim 1 wherein representing electrical characteristics of a thru test structure using a set of thru S parameters further includes measuring electrical characteristics of the thru test structure to provide the set of thru S parameters.
 3. The method of claim 1 wherein the representing electrical characteristics of a test structure including a device under test using a set of test structure ABCD parameters further comprises: measuring electrical characteristics of the test structure to provide a set of S parameters; and converting the set of S parameters into the set of test structure ABCD parameters.
 4. The method of claim 1 wherein the first set of partitioned S parameters is characterized as a set of input S parameters and the second set of partitioned S parameters is characterized as a set of output S parameters.
 5. The method of claim 4 wherein the set of input S parameters represent electrical characteristics of a two-port input network and the set of output S parameters represent electrical characteristics of a two-port output network.
 6. The method of claim 5 wherein the set of thru S parameters comprise: a thru input reflection coefficient S₁₁THRU, a thru output reflection coefficient S₂₂THRU, a thru forward transmission coefficient S₂₁THRU; and a thru reverse transmission coefficient S₁₂THRU.
 7. The method of claim 6 wherein the partitioning comprises: defining an input reflection coefficient S₁₁IN of the set of input S parameters to be equal to the thru input reflection coefficient S₁₁THRU; defining an output reflection coefficient S₂₂OUT of the set of output S parameters to be equal to the thru output reflection coefficient S₂₂THRU; and defining an output reflection coefficient S₂₂IN of the set of input S parameters to be equal to an input reflection coefficient S₁₁OUT of the set of output S parameters.
 8. The method of claim 6 wherein the partitioning further comprises: defining a magnitude of a forward transmission coefficient S₂₁IN of the set of input S parameters to be equal to a magnitude of a forward transmission coefficient S₂₁OUT of the set of output S parameters; and defining a magnitude of a reverse transmission coefficient S₁₂IN of the set of input S parameters to be equal to a magnitude of a set reverse transmission coefficient S₁₂OUT of the set of output S parameters.
 9. The method of claim 8 further comprising: defining the magnitude of the forward transmission coefficient S₂₁IN and the magnitude of the forward transmission coefficient S₂₁OUT to be equal to an Xth root of the magnitude of the thru forward transmission coefficient S₂₁THRU; and defining the magnitude of the reverse transmission coefficient S₁₂IN and the magnitude of the reverse transmission coefficient S₁₂OUT to be equal to an Xth root of the magnitude of the thru reverse transmission coefficient S₁₂THRU.
 10. The method of claim 9 wherein X corresponds to a ratio of geometric distances measurable between an input node to the device under test of the test structure and the input node to an output node of the test structure.
 11. The method of claim 9 wherein X is substantially equal to 2 when the device under test is substantially at a midpoint between the input node and the output node of the test structure.
 12. The method of claim 6 wherein the partitioning comprises: defining an angle of a forward transmission coefficient S₂₁IN of the set of input S parameters to be equal to an angle of a forward transmission coefficient S₂₁OUT of the set of output S parameters; and defining an angle of a reverse transmission coefficient S₁₂IN of the set of input S parameters to be equal to an angle of a reverse transmission coefficient S₁₂OUT of the set of output S parameters.
 13. The method of claim 6 wherein a forward transmission coefficient S₂₁IN of the set of input S parameters, a forward transmission coefficient S₂₁OUT of the set of output S parameters, and the thru forward transmission coefficient S₂₁THRU are determined to have the following relationship: ∠S ₂₁IN=∠S ₂₁OUT=(S ₂₁THRU)/X.
 14. The method of claim 13 wherein X corresponds to a ratio of geometric distances measurable between an input node to the device under test of the test structure and the input node to an output node of the test structure.
 15. The method of claim 6 wherein a reverse transmission coefficient S₁₂IN of the set of input S parameters, a reverse transmission coefficient S₁₂OUT of the set of output S parameters, and the thru reverse transmission coefficient S₁₂THRU are determined to have the following relationship: ∠S₁₂IN=∠S₁₂OUT=(∠S₁₂THRU)/X.
 16. The method of claim 6 further comprising: defining an output reflection coefficient S₂₂IN of the set of input S parameters and an input reflection coefficient S₁₁OUT of the set of output S parameters to be equal to 0+j0.
 17. The method of claim 4 wherein the set of thru S parameters are recoverable by cascading the set of input S parameters and the set of output S parameters.
 18. The method of claim 4 wherein the using comprises: cascading an inverse matrix of the first set of partitioned ABCD parameters with a matrix of the set of test structure ABCD parameters to produce an intermediate matrix; and cascading the intermediate matrix with an inverse matrix of the second set of partitioned ABCD parameters to produce a matrix of the set of device ABCD parameters.
 19. The method of claim 18, wherein the cascading an inverse matrix and the cascading the intermediate matrix each comprises performing a matrix multiplication.
 20. The method of claim 1 further comprising: providing a de-embedded representation of the electrical characteristics of the device with substantially no parasitic characteristic information in such representation; and incorporating the de-embedded representation of the electrical characteristics of the device into a circuit design library.
 21. The method of claim 20 further comprising: designing a circuit using the circuit design library.
 22. The method of claim 21 further comprising: fabricating an integrated circuit including the designed circuit. 